1. Field of the Invention
The present invention relates to heavy construction equipment and apparatus. More particularly the invention relates to crawler dozers, and an improved control apparatus for controlling the positioning of the blade of the crawler dozer.
2. Description of the Prior Art
At the present time, most crawler dozer blades are controlled by two levers, one moves in a fore and aft direction, and the other moves fore and aft and side to side. One lever controls both the lift and the tilt of the blade, while the second lever controls the angle of the blade. The lift and tilt lever motion simulates the blades' motion, but the angle lever does not simulate the angling of the blade. Because of the extra lever, the angling of the blade takes extra time for the operator of the crawler dozer to master. It also causes the operator to switch levers for the different functions.
Therefore, there has been a continuing search in the art to find a way to provide a single control lever to perform the three functions, lift, tilt and angle, and to provide for simulation with respect to each of these and particularly the angling function. Since the blade of the crawler dozer requires a minimum of three valve spools to perform the three functions, the single lever will have to control each of them. One valve spool will be needed for the lift/lower function of the blade. Another valve spool will be needed to tilt the blade with respect to a horizontal reference plane. A third valve spool will be needed to control the angle of the blade with respect to the longitudinal axis of the construction vehicle. Preferably, reciprocating the control lever back and forth in a first control direction will control the lift and lower function; reciprocating the lever left and right in a second, orthogonal, control direction will control the tilt; and twisting the control lever will simulate the change in angle of the crawler dozer blade.
Also, there is often the need to control additional functions in construction equipment. Controlling these functions requires auxillary valve spools and extra control levers. Along with the search in the art to find a way to provide a single control lever to perform the lift, tilt and angle functions of the crawler dozer blade, there has been a search directed to finding such a control mechanism to which auxillary control levers and valve spools may be added at a minimum of expense.
One attempt to control three functions with a single lever control mechanism has resulted in U.S. Pat. No. 4,938,091, issued Jul. 3, 1990, to Waggoner, et al. However, such mechanism is exceedingly complicated, is not believed to provide the simulation of the angle of the crawler dozer blade, and does not provide for the addition of auxiliary spools and levers to the control mechanism for controlling other functions as desired.
Another attempt at solving certain problems in the art has resulted in the issue of U.S. Pat. No. 4,041,976 to Roy D. Brownell on Aug. 16, 1977. The Brownell device again shows a single control lever operating three valve spools, but two of the valve spools must be operated simultaneously, and a twisting of the lever to provide control of the blade angle is not provided for. Thus, those skilled in the art have continued their search for a satisfactory single lever control mechanism which will provide for the lift and lower, tilt, and angle functions of crawler dozer blades, or perform similar functions in other construction equipment.